Apparatus for controlling the rolling of tapered sheets



Aug. 24, 1954 ZE|TL|N 2,687,052

APPARATUS FOR CONTROLLING THE ROLLING OF TAPERED SHEETS Filed Sept. 18.1951 u o i g 3; K 8 m a llh e: T

INVENTOR.

- ALEXANDER ZEITLIN ATTORNEY Patented Aug. 24, 1954 APPARATUS FORCONTROLLING THE ROLLING OF TAPERED SHEETS Alexander Zeitlin, WhitePlains, N. Y., assignor to Hydropress Inc., New York, N. Y., acorporation of Delaware Application September 18, 1951, Serial No.247,169

Claims.

This invention relates to apparatus for controlling sheet thickness inrolling mills, presses, forges and the like. In such devices a slab ofmetal is sent through the mill or press and pressure is applied theretofor the purpose of thinning out the slab into a longer sheet of uniformthickness.

The present invention however, has for one of its principal objects theprovision of apparatus whereby there may be automatically obtained afinal product in the form of a metal strip having any desired taper ineither direction.

Further objects and advantages of this invention will become apparent inthe following detailed description thereof.

The accompanying drawing is in part a side elevation of a rolling millstand and in part an electric wiring diagram, embodying the invention.

Referring to the drawing, my invention is disclosed as applied to arolling mill stand indicated generally at [0. Such stand includes sideframe members II and a central cutout portion [2 in which are slidablymounted bearing blocks l3 and I4 which form the bearing members forlarge back-up rollers Il and [8. Other bearing blocks l5 and I6,slidable in the first bearing blocks, form the bearing members for workrollers l9 and 2!. Pressure is applied to the work rollers through theback-up rollers by means of a screwdown motor M which through suitablereduction gearing 2| operates a screw 22 which applies pressure to thebearing blocks in which rollers I! are journaled. The sheet S may be fedto the mill stand on rollers 25 and it is desired that the sheet shallleave the mill stand with a predetermined taper. The simplest method ofachieving a continuous taper is either to apply continuously increasingpressure to the backup roll I! by causing the screw 22 to screwdownwardly continuously, or to start with the gap between rollers l5 andit small and continuously reduce the pressure on work roll I! bycontinuous rotation of screw 22 in the opposite direction. The firstwill give a gradually decreasing thickness to the strip as it leaves themill stand while the second will give a gradually increasing thicknessto the strip.

The problem of obtaining a uniform taper of any desired rate ofincreasing or decreasing thickness would be a simple one if equalincrements of pressure on the work rolls resulted in linear displacementof the mill frame and if there were no slippage between the strip andthe rolls. However, as is well-known in this art there are many factorswhich make the displacement of the stand non-linear, and thereforemerely operating the screw-down motor in one direction or the other at apredetermined rate will not necessarily yield a strip having a uniformtaper upon leaving the mill stand. The slippage also cannot beaccurately predetermined.

In order to obtain such uniformity of taper at any desired rate ofincrease or decrease of thickness I have provided the followingapparatus: The screw-down motor M is continuously energized from asuitable source of A. C. supply which energizes the motor field coil 30.The motor may be operated in either direction by means of switch 3|which in its lowered position as shown in the drawing makes contact at32, 33 to energize the motor in one direction, and in its raisedposition makes contact at 33, 34 to energize the motor in the reversedirection. The energization of the motor is controlled by means of aswitch 35 and the rate of speed of the motor may be controlled by arheostat 313.

By the above described mechanism the screwdown motor will runcontinuously in one direction or the other, as desired, to yield apredetermined taper in one direction or the other as the strip leavesthe mill stand. However, as stated here inbefore, uniform increments ofmovement of the screw 22 do not yield uniform increments or decrementsof mill stand pressure and it will be found that the strip as it leavesthe mill will vary from the predetermined or calculated taper. Thereforeit is necessary to provide means responsive to the thickness of thestrip as it leaves the mill stand for controlling motor M in suchdirection as to vary the rate of screw-down pres-- sure so as tocompensate for such variations in thickness. For this purpose I providemeans in the form of a potentiometer P having a contact arm C which isdriven over the coils of P to tap a varying voltage which is a functionof the length of strip which has passed out of the mill stand. Thus forexample contact C may tap from zero to 50 volts in the time that 50 ft.of a strip has passed through the mill stand. In this example eachincrement of one volt tapped by contact arm C corresponds to a foot ofmovement of the strip, and since the rate of rotation of screw 22 ispredetermined, each increment of voltage tapped by contact arm Ccorresponds to an increment of taper desired on strip S. The movement ofarm C therefore represents the desired rate of taper on strip S. Forthis purpose it is necessary that the rate of movement of contact arm Cbe correlated with the rate of movement of the strip or of the millstand. Therefore there is provided a serrated roller ii! in engagementwith the strip as it leaves the mill, the linear travel of roller 49being equal to that of the strip. The movement of roller id iscommunicated to the contact arm C through a systern of 'selsyntransmitter 4i and selsyn receiver 52 which drives through anelectromagnetic clutch s3 and a reduction gear train ir, so that contactarm C will cover a predetermined angular distance on potentiometer Pcorresponding to the length of strip s which is leaving the mill stand.

Thus the travel of contact arm C of potentiometer P represents thedesired taper. A potentiometer with constant pitch of winding wouldrepresent a linear taper. Any type of taper can be obtained by suitabledesign of the potentiometer winding. To find out Whether the desiredtaper matches the actual taper and therefore whether any change in speedof motor M is necessary, there is provided a second potentiometer Pwhose contact arm C may be driven by a galvanometer G which is energizedfrom any suitable thickness gauge, such as an X-ray re ceiver ii whichreceives the rays transmitted through the strip S by an X-raytransmitter G3. The output of the X-ray receiver may thus control thecoil [is of galvanometer G so that the degree of movement of itsarmature C is function of the thickness of the strip as it leaves themill. Thus, for example, as the thickness of the strip is continuouslydecreasing, contact arm C will be driven continuously in the samedirection as con tact arm C, and the constants of the circuit may bemade such that when the actual thickness is the same as the calculatedthickness contact arm C will tap the same voltage supplied by a source5Q as contact arm 0. The potentiometers P and P are connected inparallel to source 5% so that if contact arms C and C tap the samevoltage, there will be no output across the leads 52. However, if theactual thickness deviates from the calculated thickness in one directionor the other, there will be a diiierential voltage signal in onedirection or the other which when amplified by amplifier 5i yields anoutput which is applied to the control of motor M in such direction asto increase or decrease the rate of operation of motor M in onedirection or the other to bring the thicknessof the strip back to thecalculated thickness.

The output of amplifier 55 may be caused to control the speed of motor Mby the following mechanism: The field coil of motor M is continuouslyenergized from the D. C. source, but the armature A may be controlledfrom a standard Ward-Leonard motor control. The latter comprises a D. C.excited motor M which may be driven at a speed determined by a rheostat55, the motor driving a generator G whose field F" is excited from theD. C. source. The output of the generator is applied to the armature Aof motor M. In order that the output of amplifier 5! shall vary thespeed of motor M, the amplifier is of the type wherein the polarity ofthe output voltage corresponds to the polarity of the input voltage.Thus, a positive or negative voltage from the output of amplifier 5| maybe applied to a field coil F" to vary the voltage which is generated bythe generator G and applied to armature A. The connections are, ofcourse, such that the variation applied to armature A is in thedirection to tend to eliminate the differential between members C and C.

When the rear end of the strip is about to pass through the mill it isnecessary to return the screw 22 to its initial position. Thus in thecase where the taper has been applied by increasing the screw-downpressure continuously, it is necessary to reverse the direction ofrotation of screw 22 to raise the same. The operation of the motor iscontrolled as follows: When the forward end of the strip is about toenter the mill, a finger 6t pivoted at El rides upon the strip and istilted in a counterclockwise direction to cause contact 62 carriedthereby to engage contact 63. This energizes a coil 68 by way of leads64, 65 and a suitable source of E. M. F. 69, to pull down switch 3iagainst the action of spring 66 to close the circuit through motor M at32, 33 to cause the motor to operate in a screw-down direction. At thesame time there is energized in the circuit of coil 58 a coil it whichopens contacts H against the action of spring '12 to deenergize coil i3and permit main switch 35 to close. When the end of the strip has passedfinger 6!), spring i iwill cause contact 62 to leave contact 63 andbreak the circuit through coil E3. This will permit spring 65 to raiseswitch 3i and close contacts 33, 3 3 which will reverse the direction ofoperation of motor M. When the motor has returned to its startingposition, contacts 83 will close to permit coil is to be energized fromsource til, the deenergization of coil l0 having permitted spring E2 toclose contacts ll, and the energized coil it will open switch 35 to stopthe motor.

When the strip has left the mill, there is energized means for returningcontact arm C to its initial position. For this purpose there isprovided a finger 6 adapted to ride on the strip 8. Finger Eli ispivoted at iii and carries contact 52'. When finger fit'l rides on thestrip, contact 62 engages contact 53' to close a circuit through coilSit of electromagnetic clutch 43. The circuit of coil 93 includes leads36, it, 6'! and-source of voltage 92. When the strip S has left the:mill, spring '56- causes contact 5 to leave contact 63' and engagecontact 63". This deenergizes coil st to permit spring 93 to disengage"the clutch and energizes a motor l\ The latter drives the gearing it ina reverse direction until contact arm C engages contact 96 to close thecircuit through coil Q'l, said circuit including source of voltage 98,to break contacts 99 against the action of spring Hit. The contact arm Cwill turn to the lower end of the scale by reason of the fact that theX-ray receiver receives maximum transmission from the X-ray transmitterwhen the strip has passed through the mill.

On starting again, a strip moves to the mill stand, and the finger tilis tilted to cause contacts 52, $3 to engage to energize coil 68 to pullswitch 3i down to make contacts 32, 33 for screwdown operation of motorM. The energization of the circuit through coils t3 and iii breakscontact ii to deen rgize coil 73 and. permit switch 35 to close. Whenthe strip engages finger contact 62 leaves contact 63" and engagescontact 53' to energize the electromagnetic clutch.

A manually operated double throw switch H0 enables the operator toactuate motor M normally as a screw-down or screw-up motor, dependingupon the direction or taper desired.

The elements lit, lit, as, ll-t8 have been shown' spaced substantiallyfrom the frame II for the purposes of better illustration, but "it willbe understood that in practice these elements are positioned as close tothe frame as practicable.

Having described my invention, what I claim and desire to secure byLetters Patent is:

1. Apparatus for imparting a predetermined taper to a strip of materialas it passes through a rolling mill stand or the like, said mill standhaving Work rolls through which the strip is passed, comprising meansincluding a motor for causing one work roll to advance toward and recedefrom the other work roll, said motor being adapted to operatecontinuously as the strip passes through the stand for applying pressurecontinuously in a given direction to provide continuous increase orcontinuous decrease in pressure between the rolls to taper the strip inthe desired direction, a first actuated means actuated as a function ofthe speed of the strip through the work rolls, a second actuated meansactuated by said first actuated means as a function of the desiredtaper, a third actuated means actuated as a function of the actualtaper, a fourth actuated means actuated in accordance with thedifferential of actuation of said second and third actuated means, and afifth actuated means actuated by said fourth actuated means for varyingthe rate of application of pressure applied to the strip in a directionto eliminate the differential between the second and third actuatedmeans.

2. A device as specified in claim 1, characterized by a sixth actuatedmeans responsive to passage of the strip through the mill stand, andmeans actuated by said sixth actuated means for restoring said secondactuated means to initial position when the strip leaves the mill stand.

3. A device as specified in claim 1, which includes a seventh actuatedmeans responsive to passage of the strip through the mill stand, andmeans actuated by said seventh actuated means for restoring said workrolls to initial positions when the strip leaves the mill stand.

4. A device as specified in claim 1, which includes a seventh actuatedmeans responsive to passage of the strip through the mill stand, andmeans actuated by said seventh actuated means for reversing thedirection of operation of said motor when the strip leaves the millstand.

5. A device as specified in claim 4, which includes means for stoppingthe motor when the rolls reach their initial positions.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,339,359 Shayne et al Jan. 18, 1944 FOREIGN PATENTS NumberCountry Date 637,785 Great Britain May 24, 1950 640,762 Great BritainJuly 26, 1950 894,666 France Jan. 3, 1945

